Just as if the nation hadn`t been given a dramatic lesson in sexual harassment, just as if we haven`t spent two decades in consciousness-raising about not treading on ethnic and sexual sensitivities, comes a new epidemic of put-down jokes.

This round zings dumb blonds. And blond jokes are spreading like a flu virus around the country, especially on the computers, fax machines and office phones of white-collar types.

Some of the new jokes are variations on the old Polish genre.

Q-How many blonds does it take to change a light bulb?

A-One. She holds it to the socket and waits for the world to revolve around her.

Several, for no good reason, involve M&M candy.

Q-Why does it take a blond 13 hours to make chocolate chip cookies?

A-It takes that long to peel the M&M`s.

Q-How do you confuse a blond?

A-Give her a bag of M&M`s and tell her to put them in alphabetical order. Q-Why did the blond guy lose his job at the M&M factory?

A-He kept throwing out all the W`s.

Some of the jokes are too dumb to merit even a guilty giggle. If anything, they show how out of practice the nation has grown at developing new jokes now that most groups are off joking limits and the penalties for seeming to be so grossly insensitive can be considerable.

They also show how hungry we`ve become for new jokes to break the tedium of the office day, to serve as conversation starters, to lighten up a dull routine. In fact, the demand for fresh jokes may be increasing. Workers pushed out of smoke-free buildings to huddle outdoors on the sidewalks for their cigarette breaks need some topics for small talk besides the unreasonableness of management.

Why blonds as targets? For several reasons. So far, blonds are not included in the protected groups covered by civil-rights laws or even by the politically correct language police on college campuses-at least not yet.

Blonds are considered Caucasians, whatever their origins, and whites, especially those of northern European stock, are fair game today. Whites can legally be pushed aside in favor of less-qualified minorities-in college admissions, in hiring, in promotions and in awarding contracts. They can be blamed with impunity for the ills of the world for the last several millennia. Who better than blonds for targets of a new rash of dumb put-down jokes?

To avoid charges of sexual discrimination, most of those who tell blond jokes slip in an occasional ``he`` among the female pronouns. It`s not their fault if listeners picture Marilyn Monroe or Suzanne Somers in their minds.

But it should be noted that blond females enormously outnumber blond males by biologically impossible percentages. Anyone with the price of a bottle of Clairol can be a blond if she-he-wants. And any blond who isn`t happy with the color isn`t stuck with it longer than a quick dye job takes.

Besides, some brunets rationalize, blonds have been asking for it. Most of us grew up believing, as we repeatedly heard, that gentlemen prefer blonds and that blonds have more fun.

Brunets can`t charge hair-color discrimination, demand affirmative action and insist on fair representation among TV anchorwomen. But at least there`s a bit of comforting revenge in passing along jokes like, ``What does a blond say when she finds out she`s pregnant? `Is it mine?` `` and, ``How does a blond turn on the light after sex? Opens the car door.``

The jokes, blonds are retorting, are being concocted by brunets who have nothing to do at night while blonds are out having all the fun.

It is true that in many offices, blond jokes are most often being told by women who aren`t currently blond. ``What do you call a brunet standing between two blonds? An interpreter.``

Is this a trend to be viewed with alarm, as columnists are supposed to do, a warning that the lessons of the Clarence Thomas-Anita Hill hearings are too easily forgotten? Do blonds need their civil rights protected by new anti- discrimination laws? Should colleges be warning students that hair-ism is not politically correct and sentencing those who tell blond jokes to classes in remedial sensitivity?

But not every scrap of conversation, every silly joke has sociological implications. Not every inane thing people say is code for discrimination. Some are simply dumb jokes. And if they do carry a message, maybe it is to lighten up a little, to stop making a case of political correctness out of every trivial thing. But then, I`m a brunet.